Huge, Mysteriously Silent Satellite Spotted by Another Spacecraft

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A massive European satellite the size of a school bus that has
mysteriously stopped communicating with Earth has been spotted by
another satellite in orbit.

The giant
Envisat satellite, which is the world's largest imaging
satellite for civilian use, was photographed in stunning detail
by a French spacecraft that is also designed to snap
high-resolution images of Earth, officials with the European
Space Agency (ESA) said Friday (April 20).

The
photo of Envisat in space reveals that the $2.9 billion
spacecraft is intact and that its huge solar array is deployed.
Envisat is a huge satellite that weighs about 17,600 pounds
(8,000 kilograms). It is about 30 feet long (9 meters) and 16
feet wide (5 m), not counting the solar wing.

ESA satellite operators lost contact with the 10-year-old Envisat
on April 8 and have been trying to revive the spacecraft ever
since. As part of that rescue effort, ESA officials asked their
international partners for aid in investigating the giant
satellite's malfunction, and the French space agency CNES
volunteered time with its new Pleiades spacecraft. [ See
Envisat's photos of Earth ]

Pleiades snapped its detailed view of Envisat on April 15, when
the two spacecraft passed within 62 miles (100 kilometers) of one
another. ESA engineers are using photos from the encounter to
determine if Envisat's solar array, which is 16 feet wide (5 m)
and 46 feet long (14 m), is actually oriented in the right
position.

If Envisat is in the right position, with its solar array
collecting enough sunlight to power onboard systems, then it is
possible that the satellite is in a protective state known as
"safe mode," ESA officials said. That could make it possible to
revive the satellite, they added.

"We are really grateful to CNES for offering to acquire images of
Envisat using their Pleiades and Spot satellites," said Volker
Liebig, ESA’s Director of Earth Observation Programs, in a
statement. "Additional observations being acquired across the
globe show how the international space community has come
together to track this veteran satellite."

A ground-based radar station operated by Germany's Fraunhofer
Institute for High Frequency Physics and Radar Techniques in
Wachtberg have also captured images of the satellite to check its
orientation in space.

"These unique images will enable us to analyze Envisat's
orientation, which will indicate whether we are able to regain
contact with the satellite," said Manfred Warhaut, head of ESA’s
Mission Operations Department, in a statement.

In the United States, the U.S. Joint Space Operations Center is
keeping tabs on Envisat's orbit to verify that the satellite is
not falling out of space. Several laser-ranging ground stations
are also monitoring Envisat's orbit, ESA officials added.

Envisat launched in 2002 and successfully completed its original
five-year mission to snap
ultra-detailed views of Earth. The satellite was in the
homestretch of an extended mission when it unexpectedly went
silent. It is equipped with 10 instruments, including cameras and
radar, to observe the Earth.

The break in Envisat photographs since its communications dropout
has interrupted data services to the international agencies and
scientists that relied on the satellite's steady stream of data.
Envisat was slated to be replaced in 2013 by the first in
Europe's new fleet of Earth-monitoring Sentinel satellites.

"The Sentinels will provide the data needed for information
services to improve the management of the environment, understand
and mitigate the effects of climate change and ensure civil
security," ESA officials wrote in a statement.

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